The present invention relates to printing devices. More particularly, the present invention relates to a print media level sensor and method for use in printing devices.
Printing devices, such as inkjet printers and laser printers, use printing composition (e.g., ink or toner) to print text, graphics, images, etc. onto a print medium. Inkjet printers may use print cartridges, also known as "pens", which shoot drops of printing composition, referred to generally herein as "ink", onto a print medium such as paper, transparencies or cloth. Each pen has a printhead that includes a plurality of nozzles. Each nozzle has an orifice through which the drops are fired. To print an image, the printhead is propelled back and forth across the page by, for example, a carriage while shooting drops of ink in a desired pattern as the printhead moves. The particular ink ejection mechanism within the printhead may take on a variety of different forms known to those skilled in the art, such as thermal printhead technology.
In a current thermal system, a barrier layer containing ink channels and vaporization chambers is located between an orifice plate and a substrate layer. This substrate layer typically contains linear arrays of heating elements, such as resistors, which are energized to heat ink within the vaporization chambers. Upon heating, the ink in the vaporization chamber turns into a gaseous state and forces or ejects an ink drop from an orifice associated with the energized resistor. By selectively energizing the resistors as the printhead moves across the print medium, the ink is expelled in a pattern onto the print medium to form a desired image (e.g. picture, chart and/or text).
Printing devices typically include one or more print medium input devices, such as input trays for sheets of print media or input racks for rolls of print media. Ideally, these input devices are kept filled with an adequate supply of print media to complete required printing tasks. If not, then printing tasks will be delayed until the inadequate supply of print media is discovered and an adequate supply provided. Such delay in completing printing device jobs is problematic, particularly for larger print jobs or print jobs that are left to run unattended, such as those that are done overnight. As a consequence, printing device throughput is also reduced. Another problem of wasted print media occurs for those print jobs that run out of print media before completing and can only be started again from the beginning.
Alleviation of these problems would be a welcome improvement, thereby helping minimize delay in the completion of printing tasks, helping maximize printing device throughput, and helping prevent instances of waste of print media. Accordingly, the present invention is directed to solving those problems caused by lack of adequate print media to complete selected printing tasks. The present invention accomplishes this objective by providing a print media level sensor and method for determining a height of a stack of print media for use in printing devices. As used herein, "stack" is defined to included not only an aligned pile of print media, for example, as found in a print media input tray, but also a roll of print media as well.
An embodiment of a print media level sensor in accordance with the present invention for use in a printing device includes a print media stack follower that is configured to contact a top of a stack of print media and remain in contact with the top of the stack of print media as a height of the stack of print media changes. The print media stack follower is further configured to include encoded data representative of a plurality of heights of the stack of print media. The print media level sensor also includes a decoder that is configured to read the encoded data on the print media stack follower and to output a signal representative of the encoded data.
The above-described embodiment of a print media sensor in accordance with the present invention may be modified and include the following characteristics, as described below. The print media level sensor may further include a computing device coupled to the decoder to receive the signal representative of the encoded data therefrom. In such cases, the computing device is configured to convert the signal representative of the encoded data into a signal representative of the height of the stack of print media.
The encoded data may be formed in a body of the print media stack follower. In such cases, the encoded data may include a plurality of apertures.
The decoder may include a source configured to emit a light signal and a detector configured to receive the light signal from the source and convert the light signal into an electrical signal.
An alternative embodiment of a print media level sensor in accordance with the present invention for use in a printing device includes follower structure for tracking a height of a stack of print media. The follower structure is configured to include encoded data structure for representing a plurality of different stack of print media heights. The print media level sensor additionally includes structure for decoding the encoded data structure which is configured to output a signal representative of the encoded data.
The above-described alternative embodiment of a print media sensor in accordance with the present invention may be modified and include the following characteristics, as described below. The print media level sensor may further include computing structure coupled to the structure for decoding to receive the signal representative of the encoded data therefrom. In such cases, the computing structure is configured to translate the signal representative of the encoded data into a signal representative of the height of the stack of print media.
An embodiment of a method for determining a height of a stack of print media in accordance with the present invention for use in a printing device includes tracking a height of a stack of print media via a print media stack follower which is configured to contact a top of a stack of print media and remain in contact with the top of the stack of print media as a height of the stack of print media changes. The method additionally includes encoding data representing a plurality of different heights of the stack of print media via the print media stack follower, decoding the encoded data, and generating a signal representative of the encoded data.
The above-described embodiment of a method in accordance with the present invention may be modified and include the following characteristics, as described below. The method may further include converting the signal representative of the encoded data into a signal representative of the height of the stack of print media.